The present invention relates to fiber optics. More particularly, the present invention relates to an article for aligning and fixing an array of optical fibers in a precise position.
The Internet and emerging information services such as video-on-demand, high-definition television (HDTV) and video conferencing are creating a demand for high bandwidth (xe2x80x9cbroadbandxe2x80x9d) digital networking. Networks that incorporate optical fiber have the potential to provide the high bandwidth and data rates needed for broadband digital networking. In most such networks, the optical signals are, however, switched at lower bandwidths via electronic switching fabrics that convert the optical signals to electrical signals and, after switching, reconvert the electrical signals to the optical domain for continued transmission.
An optical switching fabric that does not convert optical signals to electrical signals and so maintains optical signal bandwidth for high-speed switching has recently been developed. See, e.g., Bishop et al., xe2x80x9cThe Rise of Optical Switching,xe2x80x9d Scientific American, pp. 88-94, January 2001. This optical switching fabric uses free-space optics to direct an optical signal from one fiber to another using MEMS-based micro-mirrors. To accommodate the large number of optical signals typically carried through a telecommunications network, the switch fabric includes two sets of large fiber arrays (input and output) and an array of micro-mirrors.
To provide low-loss free-space optical switching between input and output fiber arrays, high positional and angular tolerances are required in the fiber array. In particular, for single-mode optical fiber as is typically used in optical communication networks (core: 6-9 microns in diameter; cladding: 125 microns in diameter), positional tolerances of less than xc2x12 microns from true position and angular tolerances of less than 0.5 degrees are required for each fiber in the fiber arrays.
To achieve these tolerances, fiber arrays typically incorporate a flat faceplate with a precisely positioned array of holes. Each of the holes receives a fiber and defines its position. The diameter of the holes must be no greater than about 126 microns to provide precise alignment for a fiber having a 125 micron-diameter cladding. As a consequence of the need to insert optical fiber into holes that are only marginally larger than the fiber cladding itself, a high-precision assembly process is required.
A need therefore exists for a device that is capable of providing precise spatial and angular positioning for an array of optical fibers while receiving such fibers by a relatively low-precision process.
This need is met, in accordance with the principles of the invention, by a fiber array coupler having a frame and a plate arrangement made up of at least two parallel plates. At least one of the plates is movable within the frame.
Each of the plates includes an array of fixed size apertures. The apertures can have any one of a variety of shapes, although apertures that have a shape that tapers linearly from a relatively larger region to a relatively smaller region, such as a triangle, teardrop, etc., are advantageously used. The fixed apertures in the two or more plates align to define an array of adjustable-size apertures. The size of the adjustable-size aperture is changed by moving the movable plate, which contracts or expands the opening.
In some variations, a fiber array coupler has two plates, each having teardrop-shape apertures. The plates have a 180-degree in-plane rotation relative to one another. In one configuration, the relatively larger sections of the teardrop shape of paired apertures align, i.e., are concentric, to define a maximum size opening that is suitable for receiving bare optical fiber, i.e., fiber stripped of any jacketing, etc. In another configuration, which is obtained by moving at least one of the plates, the relatively smaller sections of the teardrop shape of paired apertures align to define a minimum size opening that is suitable for immobilizing the bare optical fiber.
In some other embodiments described herein, the apertures on each plate in the plate arrangement can have a different shape. In still other embodiments, the number of apertures on each plate in the plate arrangement can be different.